User Manual
Apollo3 Blue Datasheet
DS-A3-0p9p1 Page 726 of 909 2019 Ambiq Micro, Inc.
All rights reserved.
The window comparator enable will be discussed in a subsequent section, below. See “DMA” on page 730.
The number of samples to accumulate will also be explained in a subsequent section. See “Automatic
Sample Accumulation and Scaling” on page 726.
As described above, the channel select bit field specifies which one of the analog multiplexer channels will
be used for the conversions requested for an individual slot. See “Channel Analog Mux” on page 724.
Each of the eight conversion slots can independently specify:
▪ Analog Multiplexer Channel Selection
▪ Participation in Window Comparisons
▪ Automatic Sample Accumulation
18.2.6 Automatic Sample Accumulation and Scaling
The ADC block offers a facility for the automatic accumulation of samples without requiring core
involvement. Thus up to 128 samples per slot can be accumulated without waking the core. This facilitates
averaging algorithms to smooth out the data samples. Each slot can request from 1 to 128 samples to be
accumulated before producing a result in the FIFO. NOTE: each slot can independently specify how many
samples to accumulate so results can enter the FIFO from different slots at different rates.
All slots write their accumulated results to the FIFO in exactly the same format regardless of how many
samples were accumulated to produce the results. shows the format that is used by all conversions. This
is a scaled integer format with a 6-bit fractional part. The precision mode for each determines the format for
the FIFO data. 14-bit, 12-bit, 10-bit and 8-bit precision modes respectively correspond to 14.6, 12.6, 10.6
and 8.6 formats.
IMPORTANT: if the accumulation control for a slot is set for one sample with 14-bit precision, then the 14-
bit value coming from the ADC will be inserted into bits 6 through 19 in this format and the lower 6 bits are
zero'd. If the accumulation control for a slot is set for two samples with 8-bit precision, then the 8-bit
average integer value will be placed in bits 6 through 13, the 1 bit fractional number is placed in bit 5 and
the lower 5 fractional bits are zero'd.
Each slot contains a 21-bit accumulator as shown in Table 1065, “Per Slot Sample Accumulator,” on
page 727. When the ADC is triggered for the last sample of an accumulation, the accumulator is cleared
Table 1063: One SLOT Configuration Register
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
0
9
0
8
0
7
0
6
0
5
0
4
0
3
0
2
0
1
0
0
Reserved
#
Samples
to
Accum.
Reserved
CHANNEL
SELECT
Reserved
WINDOW_COMP
SLOT_ENABLE
Table 1064: 10.6 ADC Sample Format
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
0
9
0
8
0
7
0
6
0
5
0
4
0
3
0
2
0
1
0
0
14-bit Integer 6-bit Fraction